The present invention relates to a plug and a jack system used to interconnect computer equipment or other static electricity sensitive electronic devices through the use of multiconductor cables. Often the contacts of the cable end plugs become electrostatically charged. Because the cable and the contacts of a plug may become electrostatically charged, before a plug is plugged into an electric equipment jack, e.g., at a computer port, the plug is initially inserted into and removed from an electric discharge socket which short circuits the plug contacts and discharges the contacts and the cable. Even afterward, while the plug is being inserted into the equipment or computer, additional electric charging might occur. Accordingly, there are usually further electric discharge elements, such as diodes, in the jack for further discharging the contacts and cable.
It is an object of the present invention to provide an electric equipment jack arrangement, for a computer or other static electricity sensitive equipment, that provides protection against electrostatic charge that may be transferred from a connecting cable or plug to the equipment.
Another object of the present invention is to reduce the need for internal electronic circuitry for protecting the equipment against discharge of electrostatic build-up, caused e.g., by manipulation of a cable.
Another object of the present invention is to eliminate the need for the use of a separate device for discharging the electrostatic charge of a cable prior to connection of the cable to the equipment.
The present invention concerns an improvement in a conventional connector which provides for electrical connection to a computer or other electronic device.
The connector receives a plug having a plurality of plug contacts arranged across the plug. The connector includes a jack with a plurality of jack contacts that correspond in number and positions to the plug contacts. The jack contacts are contacted by respective contacts on the plug when the plug is fully inserted in the jack.
Grounding electrical contacts reside on the jack. According to an embodiment of the present invention, just inward of the opening into the port of the connector there is a multi-tooth comb of metal grounding contacts in the insertion path of the plug contacts. Each grounding contact corresponds to and is engageable by one of the contacts of the plug as the plug is being inserted into the connector. All of the grounding contacts are grounded. For example, the grounding contacts are electrically tied to a common discharge bar. Conventionally, a grounded shield is provided around a computer housing and around the port in the computer housing. The common discharge bar may be connected to the ground by electrically connecting it to the shield.
There is usually a reasonably high resistance between the grounding contacts and the system ground, to limit peak discharge current, to prevent arcing and to suppress electrical transients, etc. It may be between the grounding bar and the shield.
The plug contacts are connected to a cable. The cable and plug may have become electrostatically charged. The arrangement provides for a momentary electrical connection between the grounding electrical contacts and the plug contacts as the plug is initially inserted into the jack, so that the electrostatic charge in the cable is shorted to the ground. As the plug is further moved toward full insertion to the end of the jack, the arrangement provides for disconnection of the plug contacts and the grounding contacts prior to initial contact between the plug contacts and the jack contacts to prevent grounding of the jack contacts which may damage the equipment.
The grounding contacts are all spring biased to interfere with movement of the plug contacts, and the plug contacts push the grounding contacts to avoid blocking plug insertion. The grounding contacts momentarily ground and simultaneously discharge the static build-up in the cable. The shape, position and motion of the grounding contacts is such that their ground connection to the plug contacts is broken before the plug contacts engage the jack contacts.
In one embodiment, the comb of a plurality of grounding contacts is secured to the base of the jack by a folded over portion of the grounded shield around the computer housing. In another embodiment, the comb of contacts is mounted to the base by projections from the base extending into corresponding locating holes in the comb.
In yet another embodiment, a coil spring is used in lieu of the multi-tooth comb, wherein the number of coils of the spring corresponds to the number of plug contacts and the placement and spacing of the coils corresponds to the placement and spacing of the contacts. The spring is connected to the grounded shield, through the above noted resistance. Accordingly, each coil of the spring momentarily short circuits its corresponding plug contact to ground as the plug is inserted into the port.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.